Method of cleaning and maintaining potable water distribution pipe systems with a heated cleaning solution

ABSTRACT

A method of cleaning and maintaining potable water distribution systems which have reduced flow due to an increase of scale, tuberculation, sediment, and the like on the inside surface of the pipe is disclosed. An aqueous acidic cleaning solution is heated and circulated through the pipe to be treated for a sufficient time to dissolve and loosen the scale and sediment, and the spent solution containing dissolved or suspended scale and sediment is flushed from the pipe to provide a cleaned pipe with improved water flow. It is also desirable to flush the water distribution pipe system with high pressure water after the treatment to remove loosened scale and sediment that was not removed during the circulation and flushing of the treating solution.

RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.08/209,953, filed Mar. 17, 1994, which in turn is a continuation-in-partof application Ser. No. 08/036,188, filed Mar. 23, 1993, now U.S. Pat.No. 5,360,488, which also claims the benefit of application Ser. No.07/700,780, filed May 16, 1991 of which this is a continuation-in-partapplication, now U.S. Pat. No. 5,322,635, and the disclosures of all ofthese applications are incorporated herein in their entireties byreference.

BACKGROUND OF THE INVENTION

It is well known that hardness, microorganisms and suspended solids inwater sources vary widely in composition depending on the source andwill result in scale deposition including microbial tuberculation andsedimentation on surfaces wherever water is used. Scale deposition andsedimentation is particularly troublesome in water distribution pipesystems which service the residential and commercial customers ofmunicipalities, private water companies and the like along withindustrial process water distribution pipe systems as found in themining, petroleum, agriculture and the like industries. In thesesystems, the formation of scale, tuberculation and sediment can reducethe water flow through the pipe system which will limit the capacity ofthe pipe to service the requirements of the customers or to provide therequired water necessary for an industrial process, irrigation, etc. Forinstance, in municipal systems an increase in the fire risk would beobvious if the fire hydrant did not supply sufficient water toextinguish the fire due to scale, tuberculation and sediment deposits inthe feed pipe line. At some point, the water distribution pipe wouldhave to be replaced due to these restrictions at a high cost and withprolonged interruption of service.

Additionally, scale, tuberculation and sedimentation will increase thepossibility of corrosion in the water distribution pipe along withpromoting the growth of other organisms. The organisms also can be ahealth hazard, promoting corrosion and biomass which binds scale andsediment together and to the surfaces of the system. Corrosion caneventually lead to the leakage of the system and the necessity toreplace the leaking section.

The microbiological tuberculation found in water distribution pipes andwells are typically due to iron and manganese bacteria that attachthemselves to the walls of the pipe and live on the soluble iron ormanganese in the water along with other nutrients. Their spaghetti-likefeatures also allow them to trap all particulate matter which is presentin the water.

There are over 20 different iron bacteria that have been characterized.As part of their metabolism, they convert ferrous ion to ferric ionwhich results in iron oxide (rust) accumulation in the tuberculation.Manganese bacteria convert manganous ion to manganic ion which resultsin manganese dioxide accumulation in the tuberculation in the waterpipe. After generations of bacteria, the iron oxide, manganese dioxide,particulate matter and biomass accumulation on the side of the piperesults in mounds of tuberculated "growth" annalogous to a coral reef.

As the tuberculation grows, flow becomes increasingly restricted andturbulant. This leads to red water and turbidity complaints byconsumers. Restricted flow results in low pressure complaints and poorhydrant performance. Tuberculation can also interfere with valve andhydrant performance and operation. There can also be corrosive sulfatereducing bacteria that live under the tuberculation and cause pipecorrosion.

Strong acids have been used to clean water wells, however, submersiblepumps are removed prior to treatment to prevent corrosion by the acidsemployed. Also, organic acids, mixtures of mineral acids and organicacids or inhibited acid compositions have been found to clean waterwells without the necessity of removing the pumps or other equipment.These methods for cleaning water wells have involved static and surgingtreatment.

A proper cleaning and maintenance program for water distribution systemswill prevent decreased water flow capacity, corrosion and the necessityto replace the system or portions thereof. A simple and effective methodfor cleaning and maintaining these systems is needed.

SUMMARY OF THE INVENTION

This invention is directed to a method of cleaning and maintaining waterdistribution systems by employing cleaning solutions at elevatedtemperatures. Water systems having interior scale and sediment depositsare cleaned by introducing and circulating an effective amount of anaqueous treatment solution for a sufficient period of time at anelevated temperature which results in the solution, loosening andsuspension of the undesired scale and sediment. The scale is associatedwith sulfate-reducing and iron bacteria consisting primarily of ironoxide, biomass and sediment. As developed above and hereinafter, otherbacteria such as manganese bacteria may be involved in the microbialtuberculation found in water distribution pipes. Thus, "scale" as theterm is used herein, is intended to include microbial tuberculationassociated with such bacteria or other bacteria. Thereafter, the spenttreating solution containing the dissolved or suspended scale andsediment is flushed from the water distribution system to provide aclean system with improved water flow and operation. Additionally,further flushing with high pressure water will also remove additionalscale that had been loosened by the treating solution.

It has been found that potable water distribution systems may be cleanedand maintained by employing cleaning or treating solutions at elevatedtemperatures. In general, temperatures on the order of about 40° toabout 80° C. have been employed and, more particularly, from about 40°C. to about 50° C. By employing elevated temperatures, waterdistribution pipes may be cleaned of tuberculation more rapidly, forexample, tuberculated pipes cleaned at ambient temperature over a periodof about twelve hours may be cleaned in a matter of about 1-2 hourswhere the cleaning solution has been elevated in temperature to about75° to 80° C.

The cleaning solution may be acidic, neutral or basic. In the mostpreferred form, in potable water pipe systems, mineral acids or organicacids, and mixtures thereof, are employed as acidic treatment solutions.The acidic treatment solution may contain further additives such asinhibitors, chelating agents, penetrating and/or dispersing agents toassist in the removal of scale and sediment and to minimize any adverseeffects on the pipes, valves, or other system surfaces due to the acidsemployed.

This invention provides a simple, low cost and effective method ofremoving water scale and sediment from water distribution systems inorder to maintain proper water flow, operation and to prevent corrosionof the system which would require the high cost and inconvenience ofreplacement.

Other advantages and objectives of this invention will be furtherunderstood with reference to the following detailed description anddrawings.

DETAILED DESCRIPTION OF THE INVENTION

Among the acidic treatment solutions found to be useful in practicingthe method of this invention are aqueous solutions of mineral acids suchas hydrochloric, nitric, phosphoric, polyphosphoric, hydrofluoric,boric, sulfuric, sulfurous, and the like. Aqueous solutions of mono-,di- and polybasic organic acids have also been found to be useful andinclude formic, acetic, propionic, citric, glycolic, lactic, tartaric,polyacrylic, succinic, p-toluenesulfonic, and the like. The usefultreatment solutions may also be aqueous mixtures of the above mineraland organic acids.

Alkaline, acid, or neutral cleaning solutions may also be employed, asindicated above, depending upon the type of scale that needs to beremoved. Sequestering or chelating agents such as EDTA (ethylenediaminetetraacetic acid), NTA (nitrilotriacetic acid), and derivatives, i.e.,basic alkali salts, and the like have also been found to be useful inthe treatment solution in certain cases.

The acidic treatment solution may also contain acid inhibitors whichsubstantially reduce the acidic action on metal surfaces of the waterdistribution system, particularly valves, fire hydrants, etc., and thesevarious inhibitors for acids have been well documented in the patentart. Typical, but not necessarily all inclusive, examples of acidinhibitors are disclosed in the following U.S. Pat. Nos.: 2,758,970;2,807,585; 2,941,949; 3,077,454; 3,607,781; 3,668,137; 3,885,913;4,089,795; 4,199,469; 4,310,435; 4,541,945; 4,554,090; 4,587,030;4,614,600; 4,637,899; 4,670,186; 4,780,150 and 4,851,149 which areincorporated herein by reference.

The treatment solution may also contain dispersing, penetrating oremulsifying agents to assist in the removal of the scale and sediment.These surface active agents may be anionic, cationic, nonionic oramphoteric as defined in the art. Compounds such as alkyl ethersulfates, alkyl or aryl sulfates, alkanolamines, ethoxylatedalkanolamides, amine oxides, ammonium and alkali soaps, betaines,hydrotropes such as sodium aryl sulfonates; ethoxylated and propoxylatedfatty alcohols and sugars, ethoxylated and propoxylated alkylphenols,sulfonates, phosphate esters, quarternaries, sulfosuccinates, andmixtures thereof, have been found to be useful in admixture with theacid treating solution.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a laboratory test system illustrating themethod of this invention.

FIG. 2 is a diagram of a field system for cleaning a potable waterdistribution system.

With reference to FIG. 1, a laboratory test system is shown to evaluatethe removal of scale and sediment by acidic treating solutions from atest pipe sample taken from a water distribution system. This systemincludes a 15 gallon acidic treating solution reservoir 5, submersibleacidic treating solution circulation pump 6 rated at 1200 gallons perhour, 1" inlet transfer line 7, drain valve 8, heavy rubber diaphragmseals 9 for the ends of the test pipe specimen 10, 1" outlet transferline 11 and the treating solution 12. The test pipe specimen 10 ismounted at about a 30 degree angle so that the test solution willcontact essentially the entire inner pipe surface to be treated.

A laboratory test, for example, was run on a four foot section of 6"diameter pipe which had been removed from a potable water distributionsystem that had been used for over 40 years. The scale on the inside ofthe pipe consisted of tuberculated nodules of up to 1 to 11/2 inches inheight covering 100% of the inside pipe surface which had substantiallyreduced the opening inside the pipe for water to flow. Analysis of thescale indicated it consisted of primarily iron with some calcium,magnesium and manganese in the form oxides, hydroxides and carbonatesalong with fine mineral acid insoluble solids and some "biomass". Thisis typical scale associated with manganese and iron bacteria along withthe associated corrosion.

About 10 gallons of a 12.5% aqueous inhibited hydrochloric/glycolic acidsolution containing a penetrating agent was placed in the reservoir 5and circulated through the test pipe 10 for a period of 24 hours atambient temperature of about 25°-30° C. After 2 hours of circulation,particles of the scale were breaking loose and could be heard in theoutlet transfer line 11 and observed entering the reservoir 5. The colorof the treating solution also became increasingly darker withcirculation time. After 24 hours the circulation was stopped and thesystem was drained of the treating solution. The diaphragms 9 wereremoved and the inside of the test pipe was observed to be about 80%cleaned of scale and sediment solids.

On treating the test pipe with a second identical treating solution fora period of 21.5 hours, about 80% of the interior surface of the testpipe was observed to still be covered over with a scale and/or sedimentthat was a soft and paste-like semi-solid which contained some grit andcould be easily removed with a probe. The remaining scale nodules hadbeen substantially reduced in size since the end of the first treatment.It was concluded that the second treatment would probably not benecessary if a high pressure water flush was employed to remove theinsoluble soft sediment which had coated the remaining scale nodulesafter the first treatment.

With reference to FIG. 2, a field equipment and system diagram is shownwhich may be employed in the cleaning of a potable water pipedistribution system. Two 500 gallon treating solution reservoir tanks 20and 21 along with a 100 gallon per minute circulation pump 22 and sightglass 23 are mounted on a flat bed truck (not shown). A heating means22A is also shown. In this example, a 21/2 inlet pipe 24 is secured to a650 foot section of 6" water distribution pipe 25 after the main shutoff valve 26. The fire hydrant 27 and fire hose 28 were employed for theacidic treating solution return to tanks 20 and 21.

The section of pipe 25 to be treated was isolated by closing off the twowater main shut-off valves 26 and 29 along with all service line valves,typically 30 and 31. With valves 32 and 33 closed, 1000 gallons ofacidic treating solution was prepared in tanks 20 and 21. With thecoupling 34 open, the treating solution was allowed to enter the systemby opening valves 33 and 35 and turning on the circulation pump 22. ThepH of the water coming from the open coupling was then monitored until adecrease was noted which indicated the acid treating solution haddisplaced the water in the section to be treated. The circulation pump22 was turned off and the coupling 34 connected. Valves 36 and 37 werethen closed and valve 32 opened for circulation. The circulation pump 22was then started again for the treatment period. Valve 37 was closed toallow for loosened solids to accumulate in tank 20 while the treatingsolution could overflow at 38 to tank 21 which reduces the chances ofplugging during treatment.

The treating solution was then circulated in the system of FIG. 2 for aperiod of 5 hours at about 20° C. Observation of the treating solutionthrough the sight glass 23 showed an increasingly darker discolorationwith time. At the end of the treatment period, the circulation pump 22was turned off, and valves 33 and 35 were closed. The main shut-offvalve 26 was slowly opened and fresh water allowed to enter the systemuntil the treating solution was displaced as noted when the tanks 20 and21 were full. Valve 32 was then closed. The fire hose 28 was thendisconnected from the fire hydrant 27 and the main shut-off valve 26opened full to allow high pressure flushing of the treated water main25. As the flush water emerged from the fire hydrant 27 it was dark incolor with considerable tuberculation or scale and sediment solids.Flushing continued until the flush water was clean of solids for aperiod of time prior to putting the treated section of the waterdistribution system back into service.

The flow rate through the fire hydrant 27 prior to treatment had beendetermined by a Pitot Gauge to be 588 gallons per minute. Aftertreatment, the flow rate was determined to be 790 gallons per minute.This was an increase of 34.5%.

Also, improved mechanical operations of the hydrants and valves of thesystem were achieved. The flow of cleaning solution may also be reversedin the system to further improve cleaning efficiency. The above cleaningsolutions met the requirements of the National Sanitation Foundation(NSF International, Ann Arbor, Mich.), Standard 60 for potable waterdistribution systems.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Other examples of cleaning solutions may be employed as follows:

    ______________________________________                                        Preblend Ingredients    % by wt                                               ______________________________________                                        31% Hydrochloric acid in water                                                                        87.14 +/- 2%                                          70% Glycolic acid in water                                                                            5.27 +/- 0.3%                                         40% Sodium xylene sulfonate in water                                                                  2.06 +/- 0.2%                                         Triethanolamine and diethanolamine                                                                    2.96 +/- 0.2%                                         mixture (85%/15%)                                                             Water                   2.57 +/- 0.2%                                         ______________________________________                                    

In a preferred form of the invention, the above preblended cleaningsolution is used in an amount of about 12.5% by weight with water in thefield for cleaning an underground potable water distribution pipesystem. However, more generally, the solution may be employed in amountsof from about 5 to about 50% by weight with water in the field,depending upon such variables as the amount of tuberculation or scale,pipe volume to be cleaned, circulation time and other factors. Theamounts of anhydrous chemicals in a broader range of ingredients areabout 1% to 27% HCl, 0.1% to 10% glycolic acid, 0.04% to 5% sodiumxylene sulfonate and about 0.1% to 5% of thetriethanolamine/diethanolomine mixture (hereinafter referred to as"TEA").

It should be understood that the above chemical ingredients may beblended for cleaning the underground pipes, for example, hydrochloricacid may be added to a concentrate of the glycolic acid, sodium xylenesulfonate and TEA. In the potable water distribution systems, anunderground section of the pipe to be cleaned is sealed off from therest of the system. As illustrated above in FIG. 2, the cleaningsolution is then introduced from a tank into the pipe section and, ifwater is in that section of pipe, it is removed upon the introduction ofthe cleaning solution. After the cleaning solution has been introducedinto the pipe section, circulation of the cleaning solution through theunderground pipe is initiated for a sufficient period of time forsolubilization, loosening and/or suspension of the scale, tuberculationand sediments.

In the above preblends, a soap having a 1:1 stoichiometric equivalent ofthe acid (HCl and glycolic acid) and TEA base is formed with an excessof the acid. This composition has been found to work effectively in thefield for the removal of scale and tuberculation associated with ironbacteria consisting primarily of iron oxide, biomass and sediment. These1:1 soaps have also been described in the above referred to co-pendingapplication Ser. No. 07/700,780, filed May 16, 1991, now U.S. Pat. No.5,322,635 and the disclosure thereof is incorporated herein in itsentirety by reference. These soaps may be more generally categorized assoaps of mineral and/or organic acids and a base such as an amine andammonia. Further examples of these soaps include 1:1 soaps of TEA andglycolic acid (also known as hydroxyacetic acid); TEA and acetic acid;TEA and citric acid; TEA and benzoic acid; hydrochloric acid andammonia; sulfuric acid and ammonia; nitric acid and ammonia; TEA andhydrochloric acid; TEA and sulfuric acid; TEA and nitric acid; ammoniaand glycolic acid; ammonia and benzoic acid; and ammonia andp-toluenesulfonic acid. Accordingly, it will be understood that othercleaning solutions of the acidic type employing 1:1 soaps may beemployed to effectively solubilize, loosen and/or suspend the scale,tuberculation and sediment from the potable pipe in accordance with theprinciples of this invention.

The comparative effects of elevated and ambient temperatures areillustrated by the following examples.

EXAMPLE 1: CLEANING OF TUBERCULATION FROM POTABLE WATER DISTRIBUTIONPIPE AT AMBIENT AND ELEVATED TEMPERATURES

A 4" diameter potable water distribution pipe obtained from a town inArizona having up to 1" of tuberculation on the inside pipe wall was cutinto two 2-foot lengths for cleaning on the pipe testing station. Thetuberculation consisted primarily of iron oxide, manganese oxide andbiomass.

AMBIENT TEMPERATURE CLEANING

One section of the pipe was mounted in the pipe cleaning test station. Atreating solution was prepared by mixing the "Preblend Ingredients" (bywt.) of 87% muriatic acid, 5% glycolic acid, 2% sodium xylene sulfonate,3% triethanolamine/diethanolamine mixture, and water in the test stationmixing tank. The treating solution was then circulated through the pipesection at ambient temperature using an electric 110 gallon/minuteswimming pool circulating pump.

The test was run for 5 hours and the pipe section was inspected.Considerable tuberculation was still present.

The test was continued for another 33/4 hours and inspected again.Tuberculation persisted.

The test was continued for another 41/4 hours and inspected. About 95%of the tuberculation had been removed from the interior surface of thepipe section.

ELEVATED TEMPERATURE CLEANING

The second section of the pipe was mounted and cleaned in the samemanner except that a gasoline engine driven pump was employed. The pumpwas mounted on the crank case of the engine which caused the pump andthe circulating treating solution to be heated during the test. The pumpwas rated at 155 gallons per minute.

The test was run for 11/4 hours at which time the treating solution washot to the touch and estimated to be about 75-80 degrees centigrade.Upon inspection of the pipe section, the interior wall of the pipe wasessentially as clean as the pipe section cleaned at ambient temperaturefor 13 hours.

EXAMPLE 2: CLEANING OF TUBERCULATION FROM A HEAVILY TUBERCULATED WATERDISTRIBUTION PIPE BY AMBIENT TEMPERATURE CLEANING FOLLOWED BY ELEVATEDTEMPERATURE CLEANING

A 6" diameter 3' length potable water distribution pipe obtained from atown in Massachusetts having heavy tuberculation of about 2" to 21/2" inthickness (opening was about 11/2" to 2") was mounted on the pipecleaning test station. The tuberculation consisted essentially of ironand manganese oxides, biomass and sulfate-reducing bacteria. A treatingsolution was prepared as in Example 1.

Circulation was begun using the electric 110 gallon per minutecirculation pump at ambient temperature. The test was run for 11 hoursand the pipe section inspected. Heavy tuberculation remained, about 1/2"of tuberculation had been removed.

Additional cleaning composition was added to the treating solution thusdoubling the concentration of the treating solution. Circulation wascontinued at ambient temperature for an additional 7 hours and the pipesection inspected again. The tuberculation was still heavy and was about1 to 11/2" thick on the interior pipe wall.

At this point the electric pump was replaced by the gasoline engine pumpwhich heated the treating solution. The temperature of the treatingsolution was controlled by the circulation time. Circulation wascontinued for 30 minutes at which time the treating solution was 42degrees C. Circulation was then discontinued and the pipe sectiondrained of treating solution. After the treating solution cooled to roomtemperature, circulation was again started for a period of one hour atwhich time the treating solution was 50 degrees C. Circulation was againdiscontinued and the pipe section drained of treating solution. The nextday the circulation was again continued for a period of 3/4 hours atwhich time the temperature of the treating solution was about 50 degreesC. The circulation was then discontinued and the pipe section inspected.A small amount of soft residue was in the pipe which was removed with awater flush from a hose. The pipe was clean of tuberculation.

In this example, about 25% of the cross sectional area of tuberculationwas removed after 18 hours of ambient temperature treating solutioncirculation and about 75% of the cross sectional area of tuberculationwas removed by 21/4 hours of periodic elevated temperature treatingsolution circulation as described above.

In view of the above detailed description, other method variations toclean domestic and industrial water distribution systems, like houses,hotels, plants, offices, etc., will be apparent to a person of ordinaryskill in the art without departing from the scope of this invention. Themethod is especially advantageous in cleaning underground potable waterdistribution systems having tuberculation or scale associated with ironand manganese bacteria consisting primarily of iron oxide and manganeseoxides, biomass and sediment.

What is claimed is:
 1. A method for cleaning an underground waterdistribution system having a scale associated with sulfate-reducingmanganese or iron bacteria comprisingintroducing an effective amount ofan aqueous cleaning solution for the removal of said scale associatedwith sulfate-reducing, manganese or iron bacteria consisting primarilyof iron or manganese oxide, biomass and sediment from inside surfaces ofan underground water distribution system, said solution selected fromthe group consisting of acidic, neutral and basic solution, sealing offan underground section of pipe in said system for circulation of saidcleaning solution therethrough, heating said cleaning solution to anelevated temperature of about 40° C. to about 80° C., circulating saidheated cleaning solution through said underground section of pipe insaid system for a sufficient period of time for solubilization,loosening and/or suspension of said scale and sediment, flushing saidcleaning solution containing solubilized, loosened or suspended scaleand sediment from said underground pipe section in said system.
 2. Themethod of claim 1 wherein said temperature is on the order of about 40°to about 50° C.
 3. The method of claim 1 comprising the further step offlushing said system with clean water after the removal of the spentcleaning solution.
 4. The method of claim 1 comprising the further stepof flushing said system with high pressure water for the removal of anyspent cleaning solution, scale and/or sediment.
 5. The method of claim 1wherein said aqueous treatment solution is acidic.
 6. The method ofclaim 5 wherein said acid solution contains further additives selectedfrom the group consisting of acid inhibitors, chelating agents,surfactants, penetrating agents and dispersing agents, and mixturesthereof to assist in the removal of said scale and sediment.
 7. Themethod of claim 5 wherein said acid is selected from the groupconsisting of mineral and organic acids and mixtures thereof.
 8. Themethod of claim 7 wherein said mineral acid is selected from the groupconsisting of hydrochloric, nitric, phosphoric, polyphosphoric,hydrofluoric, boric, sulfuric, and sulfurous, and mixtures thereof. 9.The method of claim 7 wherein said organic acid is selected from thegroup consisting of formic, acetic, propionic, citric, glycolic, lactic,tartaric, polyacrylic, succinic, p-toluenesulfonic, and mixturesthereof.
 10. The method of claim 7 wherein said solution furthercontains an additive from the group consisting of acid inhibitors,chelating agents, surfactants, penetrating agents and dispersing agents,and mixtures thereof to assist in the removal of said scale andsediment.
 11. The method of claim 1 wherein said cleaning solution is amixture of hydrochloric acid, glycolic acid, and alkanolamine and asurfactant.
 12. The method of claim 11 wherein said mixture is employedin a preblend as the aqueous cleaning solution.
 13. The method of claim1 wherein said cleaning solution contains a soap having a 1:1stoichiometric equivalent of an acid and a base wherein said acid isselected from the group consisting a mineral acid and an organic acidand said base is selected from a group consisting of an amine andammonia, wherein an effective amount of free acid is present in thesolution to react with said scale.
 14. A method for cleaning a potableunderground water distribution pipe system having a scale associatedwith sulfate-reducing manganese or iron bacteria comprisingproviding areservoir for containing an aqueous acidic cleaning solution for theremoval of said scale associated with sulfate-reducing, manganese oriron bacteria consisting primarily of iron or manganese oxide, biomassand sediment from inside pipe surfaces of a potable underground waterdistribution pipe system, sealing off an underground section of pipe insaid system for circulation of said cleaning solution therethrough,heating said cleaning solution to an elevated temperature of about 40°C. to about 80° C., circulating said heated cleaning solution from saidreservoir through said underground pipe section and returning saidsolution to said reservoir for the removal of said scale and sediment.15. The method of claim 14 wherein said cleaning solution is a mixtureof hydrochloric acid, glycolic acid, and alkanolamine and a surfactant.16. The method of claim 14 wherein said cleaning solution contains asoap having a 1:1 stoichiometric equivalent of an acid and a basewherein said acid is selected from the group consisting a mineral acidand an organic acid and said base is selected from a group consisting ofan amine and ammonia, wherein an effective amount of free acid ispresent in the solution to react with said scale.
 17. A method of claim16 wherein said mineral acid is selected from a group consisting ofhydrochloric, nitric, phosphoric, polyphosphoric, hydrofluoric, boric,sulfuric and sulphurous, mixtures thereof, and said organic acid asselected from the group consisting of formic, acetic, propionic, citric,glycolic, lactic, tartaric, polyacrylic, succinic, poly-toluenesulfonicand mixtures thereof.
 18. The method of claim 14 wherein said reservoiris truck mounted for makeup, storage and disposal of cleaning solution.19. The method of claim 14 by sealing said pipe section between two firehydrants and circulating said cleaning solution by connecting one ofsaid fire hydrants to said reservoir for pumping said cleaning solutiontherethrough.
 20. The method of claim 14 wherein said pipe distributionsystem is domestic or industrial water distribution system.
 21. Themethod of claim 14 comprising the further step of flushing said pipesystem with clean water after the removal of spent cleaning solution.22. The method of claim 14 wherein said aqueous treatment solution meetsthe requirements of the National Sanitation Foundation Standard 60 forpotable water distribution systems.
 23. The method of claim 14 whereinsaid temperature is on the order of about 40° to about 50° C.